Exemplary embodiments of the present invention relate to a strip line cell, and more particularly, to a 4-port strip line cell for generating standard near fields for dominant electric or magnetic fields.
Existing transverse electromagnetic (TEM) lines are classified into one-port TEM lines each having input/output ports formed at one side thereof, such as a GTEM cell, a WTEM cell, a TTEM cell and an improved GTEM cell, and two-port TEM lines each having input/output ports formed at both sides thereof, such as a Crawford TEM cell (referred to as a symmetric TEM cell), an asymmetric TEM cell, a TEM for automatic measurement, a 6-port TEM cell and a strip line cell. These one- and two-port TEM lines are all used for measurement of unwanted electromagnetic waves, measurement of electromagnetic susceptibility, antenna correction, and the like. However, the one-port TEM lines support only a test for near fields, and the two-port TEM lines support not only a test for near fields but also a test for far fields. Therefore, it can be considered that the one- and two-port TEM lines are different from each other.
The two-port TEM lines may be divided into two kinds of two-port TEM lines, i.e., a waveguide cell such as a TEM cell, an asymmetric TEM cell, a TEM cell for automatic measurement or a circular TEM cell, and a strip line cell such as a straight strip line cell or a curved strip line cell. The waveguide cell generates standard electromagnetic waves by mounting an internal conductor in the inside of an external conductor and making a potential difference between the internal and external conductors. The strip line cell generates standard electromagnetic waves by mounting two flat strip lines to be exposed to the outside without being divided into external and internal conductors and making a potential difference between the two flat strip lines.
Since the internal conductor is isolated from the outside by the sealed external conductor, the waveguide cell does not have influence on external noises or is not influenced by the external noises. However, the waveguide cell should use even a first resonance frequency as a frequency used, due to the occurrence of a resonance frequency with a high Q-factor.
On the other hand, since the standard electromagnetic waves are directly generated at the outside, the strip line cell has influence on external noises or is influenced by the external noises. However, since a resonance frequency with a low Q-factor may occur due to the opened structure, the strip line cell can obtain a broadband of a frequency used.
Thus, the waveguide cell can be used in a general experiment space, but the strip line cell is recommended to be used in a sealed space such as a shielding body or chamber. In the waveguide cell, it is highly likely that the size of an object to be tested is restricted due to the sealed external conductor. On the other hand, in the strip line cell, the object to be tested is restricted by only the height between the two flat strip lines, and thus it is possible to perform measurement up to a relatively large object to be tested. In the waveguide cell, the band of a frequency used is restricted due to the occurrence of a resonance frequency with a high Q-factor. However, in the strip line cell, the two flat strip lines are exposed to the outside, and thus the band of a frequency used is further broadened thank to the occurrence of a resonance frequency with a low Q-factor.
The technical configuration described above is a background art for better understanding of the present invention, but is not a prior art well-known in the technical field pertinent to the present invention.